JP6570350B2 - Elastic roller and fixing device - Google Patents

Description

  The present invention relates to a fixing device mounted on an image forming apparatus such as an electrophotographic copying apparatus or a printer, an elastic roller used in the fixing device, and a fixing device using the same.

  A fixing device used in a toner image forming apparatus using an electrophotographic method is disposed by a heating member that is heated by a heater and abuts against an image carrying surface of a recording material to heat an image, and is opposed to the heating member. And a pressure member that forms a fixing nip (hereinafter referred to as a “nip portion”) together with the heating member.

  In recent years, for the purpose of energy saving, technical development has been performed to increase the heating efficiency of the fixing device and shorten the rise time (warm-up time) of the fixing device. One of them is to use porous silicone rubber having a large number of voids in the elastic layer of the pressure member. In such a pressure member, since heat conduction is suppressed, heat from the heating member is prevented from escaping to the other members through the pressure member, and the recording material carrying the toner is efficiently transferred at the nip portion. Can be heated.

  However, in the case of a pressure member in which heat conduction is suppressed, a nip area where the recording material does not contact when the recording material is allowed to pass (hereinafter referred to as “non-sheet passing portion”), more specifically, pressurization. There is a problem of accelerating the temperature rise at both ends in the width direction of the member, so-called “non-sheet passing portion temperature rise”.

  The temperature rise of the non-sheet passing portion is a phenomenon in which the heat from the heating member is not taken away by the recording material or the toner on the recording material in the region where the recording material is not in contact with the nip portion. Is generated when the nip is continuously passed through the nip portion. When the non-sheet passing portion temperature rises, the heating member or the pressure member constituting the fixing device may be deteriorated or deformed. Further, when a relatively large size recording material is passed through a nip portion in which a small size recording material is passed through and overheated, an offset may occur due to excessive melting of the toner.

  Therefore, Patent Document 1 discloses a needle shape in a direction along the rotation axis of the pressure roller (hereinafter referred to as “axial direction”) while improving the rising performance by dispersing the gap in the elastic layer of the pressure roller. It is described that by orienting the filler, the heat conductivity in the axial direction of the pressure roller is improved and the temperature rise of the non-sheet passing portion is alleviated.

JP 2012-37874 A

  Due to the recent demand for energy saving in the electrophotographic image forming apparatus, further improvement in the start-up performance of the fixing device, that is, further shortening of the warm-up time has been demanded.

  Therefore, the present inventors have studied to further improve the ratio of the voids in the elastic layer for the pressure roller described in Patent Document 1. The pressure roller described in Patent Document 1 injects a liquid composition containing an uncured material of addition-curable liquid silicone rubber, a needle-like filler, and a hollow body such as a microballoon or a resin balloon into a mold. Thus, an elastic layer in which the voids are dispersed while the acicular filler is oriented is formed.

  However, when a liquid composition containing a large amount of such a hollow body is injected into the mold, the orientation of the needle filler in the axial direction is hindered by the hollow body. Therefore, it is difficult to achieve both the axial orientation of the acicular filler and the further improvement in the ratio of the voids, and assuming that the acicular filler is oriented in the axial direction, the porosity is It was difficult to exceed 10%.

  On the other hand, after changing into a liquid composition containing a hollow body and injecting an emulsion of silicone rubber in which water is dispersed together with needle-shaped fillers into a mold and curing the silicone rubber in a state containing water It has been found that by dehydrating the cured silicone rubber, the needle-like filler can be oriented in the direction along the rotation axis even with an elastic layer having a high porosity.

  In this method, the silicone rubber component is added at a temperature at which moisture does not evaporate after injecting an emulsion containing an uncured addition-curable liquid silicone rubber material, water, a thickener, an acicular filler and an emulsifier into the mold. After that, a porous silicone rubber is formed through a curing and dehydrating step. In this method, it is considered that the water dispersed in the liquid silicone rubber is difficult to inhibit the axial orientation of the needle filler.

  However, when the pressure roller manufactured by such a method is used for a long period of time, the transportability of paper (recording material) becomes unstable, or wrinkles are generated on the pressure roller, so that a high-quality image can be obtained. There were cases where it was not possible. This is because, unlike the case of using a hollow body such as a glass balloon, the shell in the cured silicone rubber produced by the above method does not have a shell around the gap. Therefore, it is considered that this is because the elastic layer is easily deformed by application of pressure received when used as a pressure roller of the fixing device and release of pressure.

  Accordingly, an object of the present invention is to provide an elastic roller capable of obtaining shape stability over a long period of time while achieving both suppression of non-sheet passing portion temperature rise and high rise performance.

  Another object of the present invention is to provide a fixing device capable of efficiently heating a recording material, in which a non-sheet passing portion temperature does not easily rise, and can stably form a high-quality image. is there.

According to the present invention, an elastic roller having a shaft core body and an elastic layer formed on the peripheral surface of the shaft core body, the elastic layer including a needle-like filler and a void without a shell. Including
The porosity of the elastic layer is 20 volume% or more and 60 volume% or less, and the elastic layer has a thickness of the elastic layer from the surface of the elastic layer on the side away from the shaft core body toward the shaft core body. A region having a thickness of 30% is defined as region B, and a region having a thickness of 40% with respect to the thickness of the elastic layer in the center in the thickness direction of the elastic layer is defined as region A. The degree of orientation (A) of the needle-like filler in the axial direction of the elastic roller is 50% or less, and the degree of orientation (B) of the needle-like filler in the axial direction of the elastic roller in the region B is And an elastic roller characterized in that the degree of orientation of the acicular filler in the region A is higher (where the degree of orientation (A) is observed from the axial cross section of the elastic layer). Based on the total number of needle-shaped fillers in the portion A, the axial direction is 0 degree, and the angle θ formed with respect to the axial direction is It is an average value of the ratio (%) of the number of needle-shaped fillers within ± 5 degrees, and the degree of orientation (B) is the needle in the region B observed from the cross section in the axial direction of the elastic layer The average value of the ratio (%) of the number of needle-shaped fillers in which the axial direction is 0 degree and the angle θ made with respect to the axial direction is within ± 5 degrees with respect to the total number of the fillers. ).

  In addition, according to the present invention, there is provided a heating member and a pressure member that is disposed so as to face the heating member and pressed against the heating member, and a nip between the recording material and the pressure member. There is provided a fixing device that heats the recording material by introducing the recording material into the section and nipping and conveying the recording material, wherein the pressure member is the elastic roller described above.

  According to the present invention, it is possible to obtain an elastic roller capable of maintaining shape stability over a long period of time while achieving both suppression of temperature rise at the non-sheet passing portion and high rise performance.

  In addition, according to the present invention, it is possible to obtain a fixing device that can efficiently heat a recording material and hardly form a temperature increase in a non-sheet passing portion and can stably form a high-quality image.

1 is a cross-sectional view of an example of a fixing device according to the present invention. It is a schematic diagram ((a) perspective view (b) sectional view) of an example of an elastic roller according to the present invention. It is an enlarged view of the AB line | wire cut part in FIG.2 (b) of an example of the elastic roller which concerns on this invention. It is explanatory drawing of the definition of orientation degree. It is a schematic diagram explaining the mold forming method. It is a perspective view of an example of a nozzle. It is a schematic diagram which shows an example of a cylindrical shaping | molding die. It is a schematic diagram which shows an example of an axial center body. It is a figure explaining the non-sheet passing part of an elastic roller.

(1) Fixing Device FIG. 1 is a sectional view of an example of a fixing device according to the present invention. This fixing device is a film heating type fixing device, and a schematic configuration thereof will be described below.

  In FIG. 1, a film guide member 11 is a horizontally long film guide member having a substantially semicircular arc shape and a saddle shape in cross section and having a width direction in a direction parallel to the longitudinal direction of the substrate. The heater 12 is a horizontally long heater (a heating means which is one of the elements constituting the heating member) accommodated and held in a groove formed along the width direction at the approximate center of the lower surface of the film guide member 11. The film 13 is a film-like endless belt, and has a cylindrical shape that is loosely fitted on the film guide member 11 on which the heater 12 is mounted.

  The film guide member 11 is a molded article made of a heat resistant resin such as PPS (polyphenylene sulfite) or a liquid crystal polymer.

  The heater 12 has a configuration in which a heating resistor is provided on a ceramic substrate. The heater 12 shown in FIG. 1 includes an alumina horizontally long and thin heater substrate 12a, and a linear or thin strip Ag / layer formed on the surface side (film sliding surface side) along the longitudinal direction of the substrate. And an energization heating element (heating resistor) 12c made of Pd. The heater 12 has a thin surface protective layer 12d made of glass to cover and protect the energization heating element 12c. A temperature sensing element 12b such as a thermistor is in contact with the back side of the heater substrate 12a. The heater 12 can be controlled to maintain a predetermined fixing temperature (target temperature) by power control means (not shown) including the temperature measuring element 12b after the temperature is rapidly raised by supplying power to the energization heating element 12c.

  The film 13 is, for example, a composite layer film in which a surface layer is coated on the surface of a base film. The film preferably has a total thickness of 100 μm or less, particularly preferably 20 μm or more and 60 μm or less, in order to reduce the heat capacity and improve the quick start property of the fixing device.

Base film materials include PI (polyimide), PAI (polyamideimide),
Resin materials such as PEEK (polyether ether ketone) and PES (polyether sulfone), and metal materials such as SUS and Ni are used.

  As the material for the surface layer, fluororesin materials such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether), and FEP (tetrafluoroethylene-hexafluoropropylene copolymer) are used.

  Note that an elastic layer and / or an adhesive layer made of silicone rubber may be provided between the base film and the surface layer as appropriate.

  The pressure roller 20 is an elastic roller as a pressure member that is disposed so as to face the lower surface of the heater 12 with the film 13 interposed therebetween and is in pressure contact with the heater 12. The heater 12 and the film 13 are elements constituting a heating member, and the heater 12 functions as a heating means for the film 13.

  The pressure roller 20 is pressed to the surface protective layer 12d of the heater 12 through the film 13 with a predetermined pressure by a predetermined pressure mechanism (not shown). The elastic layer 25 of the pressure roller 20 is elastically deformed according to the applied pressure, and a nip portion N having a predetermined width necessary for heat-fixing an unfixed toner image between the surface of the pressure roller 20 and the surface of the film 13. Is formed.

  The recording material P is introduced into the nip portion N, and the recording material P is heated by being nipped and conveyed. The contact time between the film 13 and the pressure roller 20 in the nip portion N is generally about 20 to 80 msec.

  The pressure roller 20 is driven to rotate in the counterclockwise direction indicated by an arrow b at a predetermined peripheral speed when the driving force of the driving source M is transmitted through a power transmission mechanism (gear) (not shown).

  The film 13 rotates in the direction of the arrow a following the rotation of the pressure roller 20 when the pressure roller 20 is rotationally driven in the counterclockwise direction of the arrow b during image formation.

(2) Elastic Roller FIG. 2A is a perspective view of an example of the elastic roller according to the present invention, and has a configuration in which an elastic layer 25 and a release layer 26 are laminated on the peripheral surface of the shaft core body 21. .

  Next, each configuration of the elastic roller will be described.

(2-1) Shaft Core Body FIG. 2B is a cross-sectional view in the direction along the shaft core body 21 of the elastic roller shown in FIG.

  As shown in FIG. 2B, the shaft core 21 has a larger diameter at a portion where the elastic layer 25 is formed than at a portion where the elastic layer 25 is not formed.

  The configuration of the shaft core body 21 will be described in more detail with reference to FIG. 8. The shaft core body 21 includes a driving rotary shaft 22, an elastic layer forming portion 23 in which an elastic layer 25 is formed, and the other end rotating shaft 24. Become. As the shaft core body 21, for example, a surface obtained by polishing a free-cutting steel and subjected to a surface treatment such as electroless nickel plating is suitably used.

(2-2) Elastic Layer The elastic layer according to the present invention will be described in detail with reference to FIG. FIG. 3 is an enlarged view of a region cut along line AB in FIG.

  In FIG. 3, an elastic layer 25 is formed on the peripheral surface of the elastic layer forming portion 23 of the shaft core body, and a release layer 26 is further formed on the peripheral surface of the elastic layer 25. In FIG. 3, the elastic layer 25 is formed on the elastic layer forming portion 23 via the adhesive layer 28, and the release layer 26 is formed on the elastic layer 25 via the adhesive layer 27.

  The elastic layer 25 includes a needle-like filler 301 and has a large number of voids 302.

  And the porosity of this elastic layer is 20 volume% or more and 60 volume% or less.

  Further, a region 25b having a thickness of 30% of the thickness of the elastic layer is defined as a region B from the surface of the elastic layer on the side away from the shaft core to the center of the elastic layer. When the region 25a having a thickness of 40% with respect to the thickness of the elastic layer is defined as the region A, the orientation degree of the acicular filler in the region A is 50% or less, and the acicular filler in the region B The degree of orientation is higher than the degree of orientation of the acicular filler in region A.

  In FIG. 3, the figure number 25 a represents the area A, and the figure number 25 b represents the area B.

  According to the study by the present inventors, when the elastic layer has a thickness of 2 to 5 mm, the nip portion is composed of a heated fixing member and a pressure member arranged to face the fixing member. The distance reached in the thickness direction of the elastic layer, that is, the heat penetration depth, transmitted from the heated fixing member to the elastic layer when the recording material is continuously passed, is the release layer side of the elastic layer. The knowledge that it is within about 30% of the thickness of the elastic layer from the surface to the axial core direction is obtained.

  And in the elastic roller which concerns on this invention, the orientation degree of the acicular filler in the area | region B equivalent to heat penetration depth is higher than the orientation degree of the acicular filler in the area | region A.

  Therefore, when the elastic roller according to the present invention is used as a pressure member, the heat from the fixing member can be effectively diffused in the axial direction of the elastic roller. Therefore, the heat of the non-sheet passing portion of the elastic roller can be effectively diffused, and excessive temperature rise of the non-sheet passing portion that occurs during continuous sheet passing can be suppressed.

  Further, since the elastic layer has a porosity of 20% by volume or more and 60% by volume or less, thermal conduction is suppressed in the thickness direction of the elastic layer. Therefore, conduction of heat from the heating member to the pressure member in the fixing device is suppressed. Further, the apparent density of the elastic layer is lowered by the voids, and the volume specific heat of the elastic layer can be reduced. Therefore, it can suppress that the heat of a heating member is used for temperature rising of a pressurization member. As a result, the warm-up time until the temperature of the nip reaches the temperature at which the toner melts is shortened. That is, the start-up performance of the fixing device can be improved.

  Furthermore, the elastic layer according to the present invention can suppress the change in shape of the elastic layer 25 even when it is used for a long period of time by setting the orientation degree of the acicular filler in the region A to 50% or less. It is.

  The elastic layer of the pressure member in the fixing device is compressed and compressed in the nip portion, and is restored by releasing the pressure after passing through the nip.

  According to the study by the present inventors, in the elastic layer having a high degree of orientation of the needle-like filler, when compression due to pressurization and restoration by pressure release repeatedly occur than in the elastic layer having a low degree of orientation of the needle-like filler. The amount of change in the thickness of the elastic layer over time was found to be large. This is because, in an elastic layer with a low degree of orientation of the needle-like filler, the reinforcing effect on the compressive force in the thickness direction of the elastic layer is more pronounced than an elastic layer with a high degree of orientation of the needle-like filler. It is thought that.

  The distribution of the degree of orientation of the acicular filler in the thickness direction is preferably formed at least in the paper passing portion of the elastic roller. That is, in the paper passing portion of the elastic roller, the orientation degree of the needle filler in the region A is 50% or less, and the orientation degree of the needle filler in the region B is higher than the orientation degree of the needle filler in the region A. preferable.

  The paper passing portion of the elastic roller is an area where the recording material comes into contact when the recording material is passed in the longitudinal direction of the elastic roller. FIG. 9 is a diagram illustrating a paper passing portion of the elastic roller. FIG. 9A shows a paper passing portion of an elastic roller when papers of different sizes are passed with the center of the paper aligned with the center of the elastic roller. FIG. 9B shows papers of different sizes. The paper passing portions of the elastic roller in the case where the paper is passed with the end of the elastic roller aligned with the end of the elastic roller are shown. Wmax is the width of the sheet having the maximum width that can be introduced into the nip portion N, and Wmin is the width of the sheet having the minimum width that can be introduced into the nip portion N. In the present embodiment, the width Wmax of the sheet having the maximum width size is the width of the A3 sheet (short side): 297 mm, and the width Wmin of the sheet having the minimum width is the width of the A5 sheet (short side). 148 mm. A portion corresponding to the width Wmin in the longitudinal direction of the elastic roller is a region through which the paper passes through the elastic roller when any size paper is passed. A roller portion outside the width Wmin and inside the width Wmax in the longitudinal direction of the elastic roller is referred to as a sheet passing portion W, and a roller portion outside the width Wmax is referred to as a non-sheet passing portion E. In the present invention, the paper passing portion refers to the paper passing portion W + the paper passing portion S.

  The elastic layer according to the present invention is preferably a silicone rubber layer. The silicone rubber layer is preferably the only silicone rubber layer in the elastic roller.

  Although it does not specifically limit as thickness of an elastic layer, Generally, it is the range of 2 mm or more and 5 mm or less.

(2-2-1) Orientation degree of acicular filler In the elastic layer 25 according to the present invention, the orientation degree of the acicular filler in the region A is 50% or less. Moreover, the orientation degree of the acicular filler in the region B is higher than the orientation degree of the acicular filler in the region A.

  The orientation degree of the acicular filler in the region A is preferably 30% or more and 50% or less. Moreover, the orientation degree of the acicular filler in the region B is preferably 55% or more, more preferably 55% or more and 70% or less.

  The definition of the degree of orientation in the present invention will be described with reference to FIG.

  First, as shown in FIG. 4A, a sample 29 of the elastic layer 25 is cut out from the elastic roller using a razor. The sample 29 has a size of 10.0 mm in the x-axis direction, 10.0 mm in the y-axis direction, and the entire thickness of the elastic layer 25 in the z-axis direction. FIG. 4C is an enlarged perspective view of the sample 29 cut out.

  FIG. 4D is an explanatory diagram of a procedure for measuring the orientation degree of the needle filler from the sample 29.

  The silicone rubber is decomposed and removed by heating the sample 29 at 1000 ° C. for 1 hour in a nitrogen gas atmosphere using a thermogravimetric measuring device (trade name: TGA851e / SDTA; manufactured by METTLER TOLEDO).

  When the sample is baked in this way, the release layer is removed together with the silicone rubber even if the release layer is on the surface. In the sample 29 from which the silicone rubber has been removed, only the needle-like filler remains while maintaining the orientation when the silicone rubber is present. Therefore, five portions each including a region corresponding to the region A and the region B of the elastic layer 25 in the “β cross section” in FIG. 4C of the sample 29 from which the silicone rubber has been removed are observed. For the observation, a confocal microscope (trade name: OPTELICS C130; manufactured by Lasertec Corporation) is used.

  The angle of the needle filler is measured from each observation image of the “β cross section”. In addition, the needle-like filler which exists over the area | region A and the area | region B shall not be included in an observation object.

  In the observation image of the “β cross section” of the sample 29, needle-like fillers existing in a region up to about 50 μm in the depth direction from the observation surface can be observed. That is, in the observation image from the “β cross section”, it is possible to observe the state of the needle filler existing in the region from the “β cross section” to about 50 μm in the x-axis direction.

  At this time, the longitudinal direction of the roller of the elastic layer 25 (y direction in FIG. 4D) was set to 0 degree, and the angle θ of each needle-like filler was calculated. That is, the closer the angle θ of the needle-like filler is to 0 degrees, the more the orientation is in the longitudinal direction of the roller.

  From the observation image of the “β cross section”, the ratio of the angle θ within ± 5 degrees [(number of needle fillers within ± 5 degrees / number of all acicular fillers observable) × 100%] was determined, The average value of the measurement results at arbitrary five locations was defined as the degree of orientation.

(2-2-2) Void The porosity of the elastic layer 25 is 20% by volume or more and 60% by volume or less. When the porosity is 20% by volume or more, the above-described effect of shortening the rise time according to the present invention can be sufficiently obtained. Moreover, the elastic layer by which the orientation of the acicular filler was controlled can be easily shape | molded because a porosity is 60 volume% or less. Since the rising time can be shortened when the porosity is higher, the porosity is more preferably 40% by volume or more and 60% by volume or less.

  The porosity of the elastic layer 25 can be determined as follows.

  First, the elastic layer 25 is cut | disconnected in arbitrary parts using a razor. The volume at 25 ° C. is measured by an immersion specific gravity measuring device (SGM-6, manufactured by METTLER TOLEDO) (this volume is referred to as “Vall”). Next, the silicone rubber component is obtained by heating the evaluation sample subjected to volume measurement at 700 ° C. for 1 hour in a nitrogen gas atmosphere using a thermogravimetric measuring device (trade name: TGA851e / SDTA, manufactured by METTLER TOLEDO). Disassemble and remove. Let Мp be the weight loss at this time. When an inorganic filler is contained in the elastic layer 25 in addition to the needle-like filler, the residue after the decomposition / removal is in a state where the needle-like filler and the inorganic filler are mixed.

In this state, the volume at 25 ° C. is measured with a dry automatic densimeter (trade name: Accupic 1330-1, manufactured by Shimadzu Corporation) (this volume is Va). Based on these values, the porosity can be obtained from the following calculation formula (1). The density of the silicone rubber component was calculated as 0.97 g / cm ³ (this density is defined as ρp).
Formula (1)
Void ratio (volume%) = [{(Vall− (Мp / ρp + Va)} / Vall] × 100
(2-3) Release Layer The release layer 26 according to the present invention is installed on the outer surface of the elastic layer 25.

  As the release layer, a fluororesin material such as PFA capable of easily releasing the recording material is preferably used. The thickness is generally 30 to 50 microns, although it depends on the product specifications.

(3) Method for Producing Elastic Roller An elastic roller according to the present invention is an emulsion-like emulsion obtained by mixing and stirring a material containing silicone rubber uncrosslinked material, water, thickener, needle filler, and emulsifier. The base polymer in which water is uniformly and finely dispersed is formed by injecting it into a casting mold and curing, and then the water is evaporated from the base polymer. it can.

(3-1) Emulsion (3-1-1) Uncrosslinked material of silicone rubber The uncrosslinked material of the silicone rubber of the emulsion according to the present invention is a polydiorgano having two or more alkenyl groups in one molecule. It preferably contains a siloxane (hereinafter referred to as “rubber raw material A”), a polyorganosiloxane having two or more silicon-bonded hydrogen atoms in one molecule (hereinafter referred to as “rubber raw material B”), and a hydrosilylation catalyst. . The rubber raw material A and the rubber raw material B are usually prepared as separate raw materials, for example, prepared as a liquid A containing the rubber raw material A and a liquid B containing the rubber raw material B, respectively.

Here, the rubber raw material A is an alkenyl group-containing polydiorganosiloxane made of a mixture of the following rubber raw materials A1 and A2.
“Rubber raw material A1”: polydiorganosiloxane having both ends of the molecular chain blocked with alkenyl groups and having no alkenyl groups in the side chains of the molecular chain “Rubber raw material A2”: polydiorganosiloxane having two or more alkenyl groups in the side chains of the molecular chain Organosiloxane The rubber raw material B is a polyorganosiloxane having at least two silicon-bonded hydrogen atoms in one molecule.

(3-1-2) Water, thickener Water may be clean, but deionized water is generally used. Here, since water has a lower viscosity than liquid A and liquid B, it is preferable to use a thickener to facilitate mixing and dispersion, and it can be used as liquid C containing the thickener. . As the thickener, various kinds of inorganic and organic types can be mentioned. In the present invention, an inorganic thickener is preferably used. Among them, the use of an inorganic thickener composed of an organic polymer composite hydrophilic purified bentonite containing a smectite group clay mineral (“Bengel W-200U”, manufactured by Hojun Co., Ltd.) is preferable because the viscosity of the liquid C can be easily adjusted. .

  In the emulsion used for forming the elastic layer according to the present invention, there are no hollow particles having a shell conventionally used as a void forming means. For this reason, the orientation of the acicular filler in the direction along the flow direction of the emulsion is difficult to be inhibited.

(3-1-3) Needle-like filler As the needle-like filler, those having a fiber shape having a large ratio of the length L to the diameter D (hereinafter referred to as “aspect ratio”) can be used. The shape of the bottom surface of the needle-like filler may be circular or square, and any material can be used as long as it is oriented in the direction along the rotational axis of the elastic roller by a molding method. As the acicular filler, those having a thermal conductivity of 500 W / (m · K) or more and 900 W / (m · K) or less are preferable because the temperature rise of the non-sheet passing portion can be more effectively suppressed.

  Specific examples of such materials include pitch-based carbon fibers produced by firing at high temperature using petroleum pitch or coal pitch as a raw material. As a more specific shape of the acicular pitch-based carbon fiber, a diameter D (average diameter) of 5 μm or more and 11 μm or less and a length L (average length) of 50 μm or more and 1000 μm or less can be exemplified, It is easily available industrially.

  The content of the acicular filler in the elastic layer is preferably 5% to 40% by volume.

  According to the study by the present inventors, the viscosity of the emulsion depends on the blending amount of the acicular filler and water. If it mentions specially, it is possible to change the viscosity of an emulsion according to an acicular filler compounding quantity.

(3-1-4) Emulsifier The emulsified product according to the present invention is obtained by blending the emulsifier D with the above-described mixed liquid obtained by mixing the three liquids of liquid A, liquid B and liquid C at a desired ratio. Can be prepared. Various types of emulsifiers D can be used, and one or more of anionic, cationic, zwitterionic and nonionic surfactants can be used. Among these, it is particularly preferable to use a nonionic surfactant because it has little influence on the hydrosilylation reaction catalyst. The emulsifier preferably has an HLB (Hydrophile-Lipophile Balance) value of 1.5 or more and less than 6. Moreover, it is preferable that the compounding quantity of an emulsifier is 0.2-3 mass parts with respect to 100 mass parts of C liquid. The emulsifier D can also be added after mixing the three liquids of liquid A, liquid B, and liquid C. Moreover, after adding the emulsifier D to any one or several liquid of A liquid, B liquid, or C liquid, 3 liquids, A liquid, B liquid, and C liquid, can also be mixed.

(3-1-5) Viscosity of Emulsion The emulsion according to the present invention is a high viscosity liquid in which water and needle filler are emulsified and dispersed in a silicone rubber component. The viscosity depends on the emulsified state of the water to be blended and the blending amount of the acicular filler, rather than the viscosity of the base rubber. The emulsion also exhibits non-Newtonian fluid properties with different viscosities depending on the shear rate. For example, the viscosity of the emulsion according to the present invention is 30 to 150 [Pa · s] at a temperature of 25 ° C. and a shear rate of 10 [1 / s], and 20 to 100 [Pa · s] at 20 [1 / s]. s] is indicated.

(3-2) Mold Molding Method Next, the mold molding method will be described with reference to FIGS. First, the mold that constitutes the cavity will be described.

(3-2-1) Cylindrical Mold FIG. 7 is a schematic diagram of a cylindrical mold. The cylindrical mold 40 is made of a thick metal material made of stainless steel in consideration of the outer diameter accuracy of the product, deformation during use of the mold, and deformation due to heating. For example, when an elastic roller having an outer diameter of 30 mm is manufactured, the outer diameter of the molding die 40 is appropriately set to 40 mm, and the inner diameter is appropriately set according to the degree of expansion / contraction in the process of the material to be used. It is advisable to adopt a pipe shape.

  When the above-described shaft core is included in this cylindrical mold, the width of the space (cavity) formed in the mold becomes substantially the thickness of the elastic layer of the elastic roller.

(3-2-2) Nozzle A component having a function of ejecting a liquid material and injecting it into a mold is generally called a nozzle. FIG. 5 is a schematic diagram for explaining the mold and the material casting machine, and schematically shows the function of the nozzle 30. The nozzle 30 has a material outlet (gate) 32 through which the material is ejected, and a shaft core body fixing portion 33 that holds the rotating shaft of the shaft core body 21. The nozzle 30 also has a function of coaxially arranging the shaft core body 21 and the cylindrical molding die 40 by fitting with the cylindrical molding die 40 together with a cap 35 described later.

  The shapes of the gate and the shaft core fixing portion are appropriately designed according to the shapes of the cylindrical mold and the shaft core, respectively. In particular, the gate 32 preferably has a structure in which the emulsion is poured into the cavity 42 formed by the shaft core 21 and the molding die 40 without any obstacles. Inject the emulsion. At this time, by using a gate shape having a wide opening width in the rotation axis direction of the shaft core body with respect to the width of the cavity 42, the emulsion injected from the opening is the bottom surface of the elastic layer forming portion 23 of the shaft core body 21. Since the flow of the emulsion is disturbed, the elastic layer having the orientation distribution of the acicular filler in the thickness direction can be obtained more efficiently.

  FIG. 6 shows an example of the nozzle 30. In FIG. 6, the gate 32 includes a plurality of openings divided in the circumferential direction of the cavity 42 including a shaft core and a cylindrical mold. The reason why the gate 32 includes a plurality of openings is to have a structure integrated with the shaft core body fixing portion 33 that holds the shaft core body. The width of one opening of the gate 32 can be appropriately selected according to the width of the cavity 42. For example, when the width of the cavity is 3 mm, the opening width is 2 mm to 6 mm. Further, the circumferential length of one opening of the gate 32 is, for example, 20 mm to 27 mm.

(3-2-3) Cap A cap 35 is fitted and connected to the other end of the cylindrical mold 40 to which the nozzle 30 is not fitted. The cap 35 has an outlet for discharging air inside the cavity during material injection. Moreover, the shaft core body fixing | fixed part 36 holding the rotating shaft of the shaft core body 21 is provided, and it has the function to arrange | position the shaft core body 21 and the shaping | molding die 40 on the same axis | shaft with the nozzle 30. FIG.

(3-2-4) Mold Forming Method The cavity 42 is formed by combining the shaft core body 21, the cylindrical mold 40, the nozzle 30, and the cap 35. For the purpose of preventing axial misalignment in the molding process, the nozzle 30 and the cap 35 fitted to the cylindrical mold 40 are set as a die 44 integrated with an adapter part and a fixing part (not shown). Is preferred.

  As shown in FIG. 5, one end of a pipe 63 serving as an emulsion supply path is connected to the nozzle 30 via an adapter part (not shown), and the other end is connected to a measuring instrument 60 via a valve 62. ing. The emulsion 50 introduced into the measuring device 60 is transferred from the nozzle 30 to the cavity 42 via the pipe 63 by pushing down the pusher 61 attached to the measuring device 60. After the cavity 42 is filled with the emulsion 50, the mold 44 is separated from the pipe 63 and sealed.

  Next, the mold 44 filled with the emulsion is heated at a temperature at which moisture does not evaporate using a heating means such as a heating furnace or a hot platen, and the crosslinking reaction of the silicone rubber component in the emulsion proceeds. Thereby, the emulsion in the metal mold | die 44 is integrated with a shaft core body, and the silicone rubber molded object containing the acicular filler and water can be obtained. Finally, the silicone rubber molded body is taken out of the mold, and the silicone rubber molded body is dehydrated by heating at a high temperature to obtain an elastic roller having an elastic layer including needle-like fillers and voids.

  The release layer may be formed by coating on the obtained elastic roller. Alternatively, the release layer may be formed after a release layer is previously installed on the inner wall surface of the cylindrical mold by a known method. May be.

(3-3) Orientation of acicular filler Generally, the flow rate of the fluid flowing inside the pipe is different between the area near the inner wall of the pipe and the center area. Specifically, since the fluid in the region near the inner wall receives friction with the inner wall, the flow velocity is relatively lowered as compared with the fluid in the central region of the pipe.

  When this is seen about this invention, the flow rate difference arises in the thickness direction of a cavity at the time of injection | pouring of an emulsion. That is, in the vicinity of the surface of the shaft core and the vicinity of the inner wall of the mold, the flow rate is relatively decreased compared to the central region due to friction between the emulsion and the surface of the shaft core or the inner wall of the mold. As a result, it is considered that the acicular filler tends to be oriented in the flow direction by receiving shear stress in the flow direction of the emulsion in the vicinity of the shaft core and the vicinity of the inner wall of the mold where the flow velocity is reduced.

  The range in the thickness direction of the cavity in the region near the inner wall of the mold where needle-shaped fillers are easily oriented is the amount of injection (volume) per unit time of the emulsion and the direction orthogonal to the axial core body of the cavity. It is affected by the average flow rate of the emulsion traveling through the cavity determined by the cross-sectional area.

  When the average flow rate is slow, the flow rate difference in the emulsion in the thickness direction of the cavity is relatively small, and the shear stress that orients the needle filler in the axial direction is mainly in the region very close to the inner wall of the mold. Acts on the existing needle filler. Therefore, the orientation degree of the acicular filler in the region B tends to be low. On the other hand, when the average flow velocity is high, the flow velocity difference in the emulsion in the width direction of the cavity is relatively large, and shear stress that orients the needle filler in the axial direction is generated in the fluid away from the inner wall of the mold. It becomes easy to act also on the existing acicular filler. As a result, the orientation degree of the region A tends to increase.

  For this reason, in order to adjust the orientation degree of the acicular filler in the region A to 50% or less and make the orientation degree of the acicular filler in the region A lower than that in the region B, it is preferable to appropriately control the average flow velocity. For example, when an elastic layer is formed by casting a silicone rubber emulsion containing an acicular filler having an aspect ratio of about 28 and water into a cavity having a thickness in the range of 2 to 5 mm, the average in the cavity It is preferable to adjust the injection speed of the emulsion so that the flow rate is in the range of 4.0 to 8.1 [mm / sec]. When the emulsion is filled in the cavity so as to achieve the above average flow rate, the degree of orientation of the acicular filler in the region B of the resulting elastic layer can be in the range of 59 to 65%. Moreover, the orientation degree of the acicular filler in the region A can be in the range of 41 to 50%.

  The present invention will be specifically described below with reference to examples and comparative examples.

<Cylindrical mold>
Stainless steel was processed into the shape shown in FIG. 7 to form a cylindrical mold having an inner diameter of 30 mm.

<Shaft core>
Free-cutting steel (SUM) was processed into the shape of FIG. 8. For example, in Example 1, an axial core body having an outer diameter of the elastic layer forming portion of 22 mm was prepared in order to set the cavity thickness to 4 mm.

  The shaft core body in which the outer diameter of the elastic layer forming portion was changed according to the thickness of the elastic layer of the following examples and comparative examples was prepared. After applying electroless nickel plating (thickness 3 to 6 μm) on the outer surface, surface treatment is performed on any shaft core body by a known appropriate method, and the elastic layer can be suitably bonded. did.

<Needle filler>
The following pitch-based carbon fibers were used as needle-like fillers.
(Product name: XN-100-25M (manufactured by Nippon Graphite Fiber Co., Ltd.))
Average fiber diameter: 9 μm
Average fiber length L: 250 μm
Thermal conductivity 900W / (m · K)
This acicular filler is hereinafter referred to as “100-25M”.

<Preparation of an uncrosslinked silicone rubber emulsion>
As liquid C, 99 parts by mass of deionized water is added to 1 part by mass of an inorganic thickener (“Bengel W-200U”, manufactured by Hojun Co., Ltd.), and the mixture is stirred well to obtain a gel-like liquid material in advance. Prepared.

  Moreover, the nonionic surfactant (Sorbitan fatty-acid ester brand name: Ionette HLB4.3; Sanyo Chemical Industries Ltd.) was prepared as an emulsifier.

  On the other hand, as liquid A and liquid B, liquid silicone rubber (trade name: DY35-561; Toray Dow Corning Co., Ltd.), liquid A and liquid B, respectively, are used together with needle filler 100-25M. Was added to a planetary mixer at a blending amount (part by mass) shown in FIG. After kneading to some extent, the C liquid and the emulsifier were added to the mixer with the formulation shown in Table 1, and sufficiently stirred to obtain emulsions (1) to (2) containing needle fillers.

The viscosity of the obtained emulsion was measured using a rotary viscometer device (trade name: Roto Visco 1, manufactured by Thermo Fisher Scientific Co., Ltd.) and a flow curve up to a shear rate of 0 to 20 S ⁻¹ at a temperature of 25 ° C. Asked. In the ascending curve and descending curve of the obtained flow curve, the viscosity value at a shear rate of 10 s ⁻¹ was obtained, and the average value was calculated. The measurement was performed three times, and the arithmetic average of the average value was taken as the viscosity of the emulsion. The measured results are shown in Table 1.

<Release layer>
A PFA tube (Gunze Co., Ltd.) having a thickness of 50 μm was prepared.

<Example 1>
(1-1)
The stretched PFA tube was fixed inside a cylindrical mold by a known method. It was visually confirmed that the PFA tube and the cylindrical mold were in close contact.

(1-2)
A primer (trade name: DY39-067, Toray Dow Corning Co., Ltd.) was applied to the inner surface of the PFA tube of (1-1) by a known method and dried at room temperature for a predetermined time.

(1-3)
A primer (trade name: DY35-051, Toray Dow Corning Co., Ltd.) was applied to the shaft core by a known method, fired at 200 ° C. for a predetermined time, and then allowed to cool.

(1-4)
A nozzle was installed in the piping of the apparatus of FIG. 4 via an adapter, and the shaft core body (1-3) was fixed vertically to the shaft core body fixing portion of the nozzle. A cylindrical mold having the (1-2) PFA tube fixed thereto was installed so as to enclose the shaft core, and a cap and an adapter were fitted to the other end of the mold. The adapters at both ends were fixed with a fixing member, and a 4.0 mm thick cavity was formed coaxially by the above process.

(1-5)
From the lower end of the cylindrical mold fixed in (1-4), the emulsion (1) shown in Table 1 was injected at 100 grams per minute from a material injector through a pipe. After injection, the nozzle was cut off from the pipe, the adapters at both ends were sealed, and a mold in which the emulsion was hermetically sealed in the cavity was completed.

(1-6)
The mold produced in (1-5) above was put into a heating furnace set at a temperature of 90 ° C. and heated for 60 minutes.

(1-7)
The mold was removed from the heating furnace and cooled to room temperature. Next, the silicone rubber molded body integrated with the shaft core was removed from the mold.

(1-8)
The silicone rubber molded body integrated with the shaft core body was heated in a heating furnace set at a temperature of 130 ° C. for 4 hours to remove moisture from the cured molded body. Then, it heated for 4 hours with the heating furnace set to the temperature of 200 degreeC, and the molded object was fully hardened. After standing to cool, the outer dimensions of the molded body were corrected with a blade as necessary to complete an elastic roller.

<Example 2> to <Example 8>
Example except that the injection speed of the shaft core, emulsion type, and emulsion was appropriately adopted, and the emulsion was injected while changing the cavity thickness, the average flow rate of the emulsion, and the viscosity of the emulsion to the conditions shown in Table 2. An elastic roller was obtained as in 1.

The average flow velocity (mm / s) was obtained by the following calculation formula (2).
Formula (2)
Average flow rate (mm / s) = injection volume per minute of liquid compound into cavity (mm ³ / s) / cavity cross-sectional area (mm ² )
Examples except that the injection speed of the mold, the shaft core, the emulsion, and the emulsion was appropriately adopted, and the emulsion was injected while changing the cavity thickness, the injection speed, and the viscosity of the emulsion to the conditions shown in Table 2. An elastic roller was obtained as in 1.

<Comparative Example 1>
An elastic roller was obtained in the same manner as in Example 1 except that the injection speed was 200 g / min.

<Comparative example 2>
An elastic roller was obtained in the same manner as in Example 8 except that the injection speed was 25 g / min.

<Evaluation of elastic roller>
The evaluation shown below was performed about each produced elastic roller. The evaluation results are summarized in Table 3.

(Degree of orientation)
The orientation degree of the acicular filler in the elastic layer of each elastic roller was determined according to the definition of the orientation degree described above.

(Non-paper passing part temperature rise)
Each elastic roller is used as a pressure roller and mounted on a printer (trade name: LBP-5910, manufactured by Canon Inc.) on which the film heating type fixing device shown in FIG. 1 is mounted. The temperature was evaluated.

The peripheral speed of the pressure roller mounted on the fixing device was adjusted to be 234 mm / sec, and the heater temperature was set to 220 ° C. The paper passed as the recording material P carrying the toner T in the nip portion N of the fixing device is letter (LTR) size paper (75 g / m ² ). The film 13 of the paper passing portion W (region where the LTR size paper is not in contact) when 500 sheets of the paper are continuously fed so that the longitudinal direction of the paper is parallel to the longitudinal direction of the pressure roller. The surface temperature was measured. The temperature rise suppression effect of the non-sheet passing portion according to the present invention is the non-sheet passing portion temperature of the heating member (about 270 ° C.) when a fixing device using a pressure roller having a general elastic layer is used. ) Is lower.

(Rise performance)
Using the above fixing device, the time from when the heater switch was turned on until the surface temperature of the film 13 reached 180 ° C. was measured in the idling state where no paper was passed.

(Thickness change of elastic layer)
Using the above fixing device, an idling test for a total of 300 hours was performed. The thickness of the elastic layer was measured before and after the durability test. In addition, the thickness of the elastic layer is the same as that shown in FIG. 4A for the elastic roller before and after the durability test according to each of the examples and comparative examples. The thickness was determined by observing at a magnification of 50 times using an optical microscope (trade name: VHX-200; manufactured by Keyence Corporation), and the average value was taken as the thickness of the elastic layer.

11 Film guide member 12 Heater 13 Film 20 Pressure roller (elastic roller)
21 Axle core 25 Elastic layer 25a Region A
25b Region B
26 Release layer 301 Needle-like filler 302 Void

Claims (10)

A shaft core,
An elastic layer formed on the peripheral surface of the shaft core;
An elastic roller having
The elastic layer includes a needle-like filler and a void having no shell,
The porosity of the elastic layer is 20% by volume or more and 60% by volume or less,
A region having a thickness of 30% of the thickness of the elastic layer is defined as a region B from the surface of the elastic layer away from the shaft core toward the shaft core.
When a region having a thickness of 40% of the thickness of the elastic layer at the center in the thickness direction of the elastic layer is defined as region A,
The degree of orientation (A) in the axial direction of the elastic roller of the acicular filler in the region A is 50% or less, and
An elastic roller characterized in that the degree of orientation (B) of the needle filler in the region B in the axial direction of the elastic roller is higher than the degree of orientation of the needle filler in the region A;
However, the degree of orientation (A) is based on the total number of the needle-like fillers in the region A observed from the cross section in the axial direction of the elastic layer. Is the average value of the ratio (%) of the number of needle-shaped fillers that is within ± 5 degrees,
The degree of orientation (B) is defined with respect to the axial direction, with the axial direction being 0 degrees with reference to the total number of the needle-like fillers in the region B observed from the cross section in the axial direction of the elastic layer. The angle θ is an average value of the ratio (%) of the number of needle-shaped fillers within ± 5 degrees.   The elastic roller according to claim 1, wherein the elastic layer is a silicone rubber layer.   The elastic roller according to claim 2, wherein the silicone rubber layer is the only silicone rubber layer in the elastic roller. In the sheet passing portion of the elastic roller, pre Sharing, ABS Mukodo (A) is 50% or less,
The elastic in the sheet passing portion of the roller, prior Sharing, ABS Mukodo (B) is an elastic roller according to any one of high claims 1 to 3 than in the previous Sharing, ABS Mukodo (A). Elastic roller according to any one of claims 1 to 4 before Sharing, ABS Mukodo (B) is 55% or more.   The elastic roller according to any one of claims 1 to 5, wherein the elastic layer has a porosity of 40% by volume or more and 60% by volume or less.   The elastic roller according to any one of claims 1 to 6, wherein the needle-like filler is pitch-based carbon fiber.   The elastic roller according to any one of claims 1 to 7, wherein the needle-like filler has a diameter of 5 µm to 11 µm and a length of 50 µm to 1000 µm.   The elastic roller according to any one of claims 1 to 8, wherein a thickness of the elastic layer is 2 mm or more and 5 mm or less. A heating member, and a pressure member disposed opposite to the heating member and pressed against the heating member, and a recording material is introduced into a nip portion between the heating member and the pressure member. A fixing device that heats the recording material by nipping and conveying, wherein the pressure member is the elastic roller according to any one of claims 1 to 9 .

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